Chitosan-Based Polymer Nanocomposites for Environmental Remediation of Mercury Pollution.

Mercury is a well-known heavy metal pollutant of global importance, typically found in effluents (lakes, oceans, and sewage) and released into the atmosphere. It is highly toxic to humans, animals and plants. Therefore, the current challenge is to develop efficient materials and techniques that can be used to remediate mercury pollution in water and the atmosphere, even in low concentrations. The paper aims to review the chitosan-based polymer nanocomposite materials that have been used for the environmental remediation of mercury pollution since they possess multifunctional properties, beneficial for the adsorption of various kinds of pollutants from wastewater and the atmosphere. In addition, these chitosan-based polymer nanocomposites are made of non-toxic materials that are environmentally friendly, highly porous, biocompatible, biodegradable, and recyclable; they have a high number of surface active sites, are earth-abundant, have minimal surface defects, and are metal-free. Advances in the modification of the chitosan, mainly with nanomaterials such as multi-walled carbon nanotube and nanoparticles (Ag, TiO2, S, and ZnO), and its use for mercury uptake by batch adsorption and passive sampler methods are discussed.

Quantification of some ARVs' removal efficiency from wastewater using a moving bed biofilm reactor.

To date, in South Africa alone, there are an estimated 4.5 million people receiving antiretroviral (ARV) therapy. This places South Africa as the country with the largest ARV therapy programme in the world. As a result, there are an increasing number of reports on the occurrence of ARVs in South African waters. Achieving efficient and bio-friendly methods for the removal of these pollutants is considered as a concern for environmental researchers. This study aims at studying the efficiency of a moving bed biofilm reactor (MBBR) system for removing ARVs from wastewater. A continuous-flow laboratory scale system was designed, built, installed, and operated at a carrier filling rate of 30%, an organic loading rate of 0.6 kg COD/m3.d-1 OLR, a hydraulic retention time of 18h, and a 27.8 mL/min flow rate. The systems were monitored over time for the elimination of conventional wastewater parameters i.e., Biological Oxygen Demand, Chemical Oxygen Demand, and nutrients. The results showed that the MBBR system as a bio-friendly method has high efficiency in removing Nevirapine, Tenofovir, Efavirenz, Ritonavir and Emtricitabine from the synthetic influent sample with an average removal of 62%, 74%, 94%, 94% and 95%, respectively, after 10 days of operation.

Synthesis, Characterization and Antimicrobial Activity of Zinc Oxide Nanoparticles against Selected Waterborne Bacterial and Yeast Pathogens.

The disinfection of wastewater using nanoparticles (NPs) has become a focal area of research in water treatment. In this study, zinc oxide (ZnO) NPs were synthesized using the microwave heating crystallization technique and characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Qualitative well diffusion and quantitative minimum inhibitory concentration (MIC) tests were conducted to determine the antimicrobial activity of ZnO NPs against selected waterborne pathogenic microbes. FTIR spectral studies confirmed that the binding of urea with Zn occurs through Zn-O stretching. XRD confirmed the crystallized identity in a hexagonal ZnO wurtzite-type structure. The formation of zones of inhibition and low MIC values in the antimicrobial analysis were indicative of the effective antimicrobial activity of zinc oxide nanoparticles against the test microorganisms. The application of metallic nanoparticles in water treatment could curb the spread of waterborne microbial diseases.

A Review on Conventional and Advanced Methods for Nanotoxicology Evaluation of Engineered Nanomaterials.

Nanotechnology can be defined as the field of science and technology that studies material at nanoscale (1-100 nm). These nanomaterials, especially carbon nanostructure-based composites and biopolymer-based nanocomposites, exhibit excellent chemical, physical, mechanical, electrical, and many other properties beneficial for their application in many consumer products (e.g., industrial, food, pharmaceutical, and medical). The current literature reports that the increased exposure of humans to nanomaterials could toxicologically affect their environment. Hence, this paper aims to present a review on the possible nanotoxicology assays that can be used to evaluate the toxicity of engineered nanomaterials. The different ways humans are exposed to nanomaterials are discussed, and the recent toxicity evaluation approaches of these nanomaterials are critically assessed.

Descriptive data on trichloroethylene and Congo red dye adsorption from wastewater using bio nanosponge phosphorylated-carbon nanotube/nanoparticles polyurethane composite.

The availability and quality of water resources is currently the primary concern in Southern Africa. The challenge is to improve or develop water treatment materials or methods to solve this problem of potable water scarcity. Hence, this article presents the analyzed data, which are supplementary data information on the study of bio nanosponge phosphorylated-carbon nanotube/nanoparticles polyurethane composite (pMWCNT/ß-CD/TiO2-Ag) as polymeric nanobiosorbent, for water treatment. The developed polymeric nanobiosorbent (pMWCNT/ß-CD/TiO2-Ag) was synthesized using combined methods of amidation reaction, cross polymerization, and sol-gel process. The removal of water pollutants (trichloroethylene (TCE) and Congo red (CR) dye) was conducted by the batch adsorption method. The conditions used during the adsorption experiments and methods (applied to quantify the water samples after adsorption studies) are described. Additional data obtained on the effect of pH, isotherm, kinetic, and thermodynamic studies are also illustrated.

Recent development in antimicrobial activity of biopolymer-inorganic nanoparticle composites with water disinfection potential: a comprehensive review.

Nowadays, water-borne diseases including hepatitis remain the critical health challenge due to the inadequate supply of potable and safe water for human activities. The major cause is that the pathogenic microorganisms causing diseases have developed resistance against common techniques used by sewage water treatment plants for water disinfection. Therefore, there is a need to improve these conventional water treatment techniques by taking into consideration the application of nanotechnology for wastewater purification. The main aim of this paper is to provide a review on the synthesis of biopolymer-inorganic nanoparticle composites (BINCs), their used as antimicrobial compounds for water disinfection, as well as to elaborate on their antimicrobial mechanism of action. The microbial properties affecting the activity of antimicrobial compounds are also evaluated.

Chitosan nanocomposites for water treatment by fixed-bed continuous flow column adsorption: A review.

Nowadays, access to clean water sources worldwide and particularly in Southern Africa is inadequate because of its pollution by organic, inorganic, and microorganism contaminants. A range of conventional water treatment techniques has been used to resolve the problem. However, these methods are currently facing the confronts posed by new emerging contaminants. Therefore, there is a need to develop simple and lower cost-effective water purification methods that use recyclable bio-based natural polymers such as chitosan modified with nanomaterials. These novel functional chitosan-based nanomaterials have been proven to effectively eliminate the different environmental pollutants from wastewater to acceptable levels. This paper aims to present a review of the recent development of functional chitosan modified with carbon nanostructured and inorganic nanoparticles. Their application as biosorbents in fixed-bed continuous flow column adsorption for water purification is also discussed.

Spectroscopic characterization and antimicrobial activity of nanoparticle doped cyclodextrin polyurethane bionanosponge.

This study reports on the spectroscopic characterization and antimicrobial potency of polyurethane cyclodextrin co-polymerized phosphorylated multiwalled carbon nanotube-doped Ag-TiO2 nanoparticle (pMWCNT-CD/Ag-TiO2) bionanosponge nanocomposite. The synthesis of pMWCNT-CD/Ag-TiO2 bionanosponge nanocomposite was carried out through the combined processes of amidation and polymerization reactions as well as the sol-gel method. The native nanosponge cyclodextrin and phosphorylated multiwalled carbon nanotube-nanosponge CD (pMWCNT-CD) polyurethanes were also prepared, and their antimicrobial activities carried out for comparison purposes. The synthesized bionanosponge polyurethane materials were characterized using Fourier-transform infrared (FTIR) spectroscopy, Laser Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to give clear information regarding their structural, and dynamic physicochemical properties. The potency tests of the synthesized compounds were carried out against three bacterial strains Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and two fungal representatives Aspergillus ochraceus and Aspergillus fumigatus, using the disc diffusion method. Micro dilution and agar plating were used to determine the minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC), respectively. The results obtained revealed that pMWCNT-CD/Ag-TiO2 exhibits superior antibacterial and antifungal activities when compared to the other bionanosponge polymers tested. Thus, the bionanosponge polyurethane pMWCNT-CD/Ag-TiO2 nanocomposite can be considered as an active antimicrobial compound (AMC).

Nanosponge cyclodextrin polyurethanes and their modification with nanomaterials for the removal of pollutants from waste water: A review.

Water is a worldwide vital resource for sustaining life and due to the pollution of water by different classes of pollutants (inorganic, organic and pathogens), many ongoing studies in water purification remain a critical issue to governments, scientists and industries. The challenge is to develop a water purification technology which will be effective at removing these contaminants simultaneously and reducing their concentrations to ultra low levels from waste water. This review article serves to give an overview on cyclodextrin nanosponge adsorbents which have already been used for water treatment. The modification of these cyclodextrin nanosponges with existing adsorbent nanomaterials (carbon nanotubes, TiO2 and silver nanoparticles) and the factors affecting the adsorption capacity of these nanosorbents are discussed. The nanotoxicity of these engineered nanosorbents material is also addressed since nanotoxicity is a major concern to human health and environment.